For healthy reasons, various non-invasive medical diagnosis methods are becoming widely accepted by people. Among the various non-invasive medical diagnosis methods, Computed Tomography (CT) is already generally used. An indispensable component used in CT equipments is an X-ray sensor.
FIG. 1 illustrates a basic configuration of an X-ray sensor. The X-ray sensor 12 comprises a plurality of scan lines 15, a plurality of data lines 16 and a plurality of sensing elements, each of the sensing elements comprises a photodiode 13 and a field effect transistor (FET) 14. The gate of the FET 14 is connected to a corresponding scan line 15 of the X-ray sensor 12, the drain of the FET 14 is connected to a corresponding data line 16 of the X-ray sensor, and the source of the FET 14 is connected to the photodiode 13. One end of the date lines 16 is connected to a data readout circuit 18 via a connecting pin 17.
The working principle of the above X-ray sensor is as follows: the X-ray sensor 12 supplies a scan drive signal via the scan lines 15 to control the ON/OFF state of the FET 14 of each sensing element. When the FET 14 is turned on, the photocurrent signal generated by the photodiode 13 is output sequentially via the data line 16 connected to the FET 14 and the data readout circuit 18, and capturing of the photocurrent signal is realized by controlling timing of signals on the scan line 15 and the data line 16. That is to say, the capturing of the photocurrent signal generated by the photodiode 13 is controlled by controlling the ON/OFF state of the FET 14.
Currently, X-ray sensors generally employ a thin film transistor (TFT) plate configuration. Such an X-ray sensor may have many layers in its cross section. For example, each sensing element comprises a substrate, a gate electrode layer, a gate insulating layer, an active layer, a source electrode and a drain electrode layer, a passivation layer, PIN junction of the PIN photoelectric sensor, a transparent electrode window layer, and a bias line layer as well as a light-shield strip layer. Detailed patterning layers may differ from each other for different X-ray sensors, depending on the specific configuration of the sensors.
Individual patterning layers of the X-ray sensor are generally formed via patterning processes and each patterning process generally comprises steps of masking, developing, exposing, etching and peeling. That is to say, multiple patterning processes are needed to realize multiple patterning layers of the sensor. For example, 9 to 11 patterning processes are needed to form a multi-layer X-ray sensor as described above, thereby 9 to 11 masks are required, which makes the fabrication cost high and the process complicated and the production capacity difficult to increase.